A decimal point separates the integer and fractional parts of a floating point value. The character being used may need to alter depending on the locale of the hosting environment.
If your national language routines change the formatting of numbers, be aware that commas and dots mean different things.
A dot is really a decimal point. A comma is a thousands separator.
In some formatting regimes, thousands may be separated by a space character and a comma may be used in place of a dot (or vice versa).
Note also that it is a convention in financial reports to show negative values in parentheses but as a positive value.
All of this can make it difficult to parse numeric values that a user may enter into a text field.